1. Field of the Invention
The present invention is directed to an improved cylinder lock assembly. In particular, the present invention discloses a cylinder lock assembly that maintains a rotational coupling between a cylinder plug and a tailpiece in the event that the connection between them is forcibly breached.
2. Description of the Related Art
Cylinder lock assemblies are known in the art. In general, a cylinder lock assembly may comprise a cylinder plug and a tailpiece. The tailpiece is normally operatively coupled to a deadbolt, latch or the like on one end and to the cylinder plug on the other end, thereby coupling the cylinder plug to the deadbolt or latch. When the cylinder plug is rotated—e.g., by inserting and turning an appropriate key—it causes the tailpiece to rotate, which then causes a reciprocal retraction or extension of the deadbolt or latch. Typically, the cylinder plug, and therefore the tailpiece, can only rotate when the proper key is inserted into the plug. A problem associated with this kind of lock, however, is that a tailpiece may be made to rotate independantly of a cylinder plug by forcibly disconnecting the without the insertion of the proper key.
FIG. 1 shows a conventional cylinder lock assembly. The lock includes a cylinder plug 10 that is rotatably held within a housing (not shown) and includes a front end 14 and a rear end 12. Exemplary cylinder locks of the type shown are described in the following patents assigned to Medeco Security Locks, Inc.—the respective disclosures of which are hereby incorporated by reference: U.S. Pat. No. 3,499,302 Spain et al (1970) U.S. Pat. No. 3,722,240 Spain et al (1973), U.S. Pat. No. 4,635,455 Oliver (1987), U.S. Pat. No. 5,289,709 Field (1994), U.S. Pat. No. 5,419,168 Field (1995), U.S. Pat. No. 5,570,601 Field (1996), U.S. Pat. No. 5,615,565 Field (1997), U.S. Pat. No. 6,023,954 Field (2000), and U.S. Pat. No. 6,477,875 Field et al. (2002).
As is conventional with cylinder locks of the type shown, cylinder plug 10 may include a plurality of radially arranged tumbler shafts 16 for receiving tumbler pins (not shown). A tailpiece 20 is connected to the rear end 12 of the cylinder plug by means of screws, bolts, or other suitable fasteners 1 extending through fastener holes 22 of a tailpiece retainer (retainer plate) 18 and into a fastener-receiving hole 24 formed in the cylinder plug 10. The cylinder lock is operated by means of a key (not shown) inserted into a keyway opening at the front end 14 of the cylinder plug to thereby rotate the cylinder plug 10 about its longitudinal axis within the housing. Rotation of the cylinder plug 10 causes a corresponding rotation of the tailpiece 20 and tailpiece retainer plate 18. The tailpiece 20 is coupled to a bolt or a door-latching mechanism (e.g., a lockset) in a known manner to cause reciprocal retraction and extension of the bolt or latch due to the rotation of the tailpiece 20.
It has been suggested that the cylinder lock shown in FIG. 1 can be breached by inserting a thin rigid object (e.g., a punch) into the keyway, such that the object extends through the rear end 26 of the keyway and against the retainer plate 18 or the end of the tailpiece 20, and thereafter applying a sharp impact force to the rigid object, thereby shearing or otherwise disabling the fastener(s) 1 connecting the tailpiece retainer plate 18 to the cylinder plug 10. With the tailpiece retainer plate 18 disconnected from the cylinder plug 10, the tailpiece retainer plate 18 and the tailpiece 20 can be rotated independently of the cylinder plug 10. Accordingly, if a narrow tool can be inserted into the keyway to grasp and rotate the tailpiece retainer plate 18 and tailpiece 20, the bolt or door latching mechanism can be retracted without rotating the cylinder plug 10, and thus the lock can be bypassed without a key.
Thus, there is a continued need for new and improved cylinder lock assemblies that prevent the deadbolt or latch from being operated even when the tailpiece has been forcibly disconnected from a cylinder plug.